Train isn't moving, then moving (9)

I believe the answer is:

intransit

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'moving' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'train isn't moving' is the wordplay.
'moving' indicates anagramming the letters (letters are moved around).
'train'+'isnt'='trainisnt'
'trainisnt' is an anagram of 'INTRANSIT'.

'then' is the link.

Can you help me to learn more?

(Another definition for intransit that I've seen is " on the way".)

I've seen this clue in The Daily Express.

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